This invention relates in general to brake systems for motor vehicles, and in particular to fluid pressure operated boosters for vehicle braking systems.
Conventional vehicle brake systems are constructed such that the braking force developed by the system is generally proportional to the force applied by the vehicle operator on a vehicle brake pedal. The pedal is linked to a piston in a master cylinder which moves to pressurize the fluid of the brake system, and thus actuate the individual wheel brakes. Generally, in order to provide a sufficiently high pressure to operate the wheel brakes without requiring an excessive effort by the operator, most vehicles include a "boosted" power brake system wherein the force applied to the brake pedal by the operator is amplified or boosted before being applied to the master cylinder. In automobiles and light trucks, this is typically accomplished by incorporating either a vacuum or hydraulically operated boost piston assembly between the brake pedal and the master cylinder.
Vacuum operated boost piston assemblies utilize the pressure differences between the atmosphere and the vehicle's engine vacuum to develop a force across a boost piston or diaphragm. The force developed by this differential pressure across the boost piston may be many times that which could be developed by the operator by pressing against the pedal, and is applied to the piston of the master cylinder to actuate the brakes.
Hydraulic boost piston assemblies utilize the pressure developed by a hydraulic system, such as the vehicle's power steering system, to apply a force to a boost piston. The force applied by the hydraulic system to the boost piston, like the vacuum boost system may be many times that which could be applied by the operator of the vehicle without a boost system. The increase force applied to the piston of the master cylinder generates higher braking system operating pressures for a given pedal force input.